Dual-action power-operated abrading tool



DEC. 31, 1968 M SHEPS DULACTION EOWER-OPERATED ABRADING TOOL Sheet of Filed March 28, 1966 FIG. I

FIG. 2

FIG. 3

MARTIN I. SH EPS fw/fw ATTORNEY M. l. sHEPs 3,418,761

DUAL-ACTION POWER-OPERATED ABRADING TOOL Sheet 2 of 2 INVENTOR MARTIN I. SHEPS BY /wm ATTORNEY Dec. 31, 1968 Filed March 28, 1966 United States Patent O 3,413,761 DUAL-ACTION POWER-g-IERATED ABRADING Martin I. Sheps, Baltimore, Md., assignor to The Black and Decker Manufacturing Company, Towson, Md., a corporation of Maryland Filed Mar. 28, 1966, Ser. No. 538,005 Claims. (Cl. 51-170) ABSTRACT OF THE DISCLOSURE A portable power-operated abrading tool has a dual action by means of which the platen is adapted for either orbital motion or straight-line reciprocation. The mechanism includes a pivot arm between the housing and the platen, and the driving eccentric is operatively connected to the arm intermediate the ends thereof. One end of the arm is pivotably mounted on the platen, and the other end of the arm is free. A combined guiding and selective clamping means is mounted on the platen, beyond the free end of the pivot arm, for slidably receiving and supporting the arm in its normal unrestrained position. This combined guiding and selective clamping means has a manually-actuated means integrally included therein for selectively lclamping the free end of the pivot arm in a vertical plane which is substantially parallel to the vertical axis of the driving eccentric, but ofset radially therefrom. In this manner, the free enfd of the pivot arm may be restrained, thereby selectively converting the straight-line reciprocation of the platen into an orbital-type of reciprocation.

The prior art In the prior art, there exists various types of dual action portable electric Sanders or related abrading-type tools. These tools usually employ a generally rectangular platen which is disposed below the tool housing and is resiliently mounted thereto. Some dual-action tools employ a pivot arm between the housing and the platen. This pivot arm has a pair of ends, one of which is pivotably mounted to the platen, and the other of which is free. A bearing may be mounted on the pivot arm intermediate its ends, and a driving eccentric journaled in the bearing along a vertical axis. Accordingly, the pivot arm oscillates in a horizontal plane above the platen, and thereby functions as an intermediate driving member, with the platen experiencing a substantially straight-line reciprocation. If the free end of the pivot arm is clamped or restrained against further movement or oscillation, then the straight-line reciprocation of the platen is converted to an orbital reciprocation. Accordingly, one of the prior art concepts employs resilient restraint for the free end of the pivot arm. This resilient restraint is provided by a coil spring piloted on a rod and seated between axially-spaced washers, one of which is secured on the rod. One end of the rod carries a resilient pad received within a socket formed in the free end of the pivot arm. T'he spring-loaded rod restrains the free en'd of the pivot arm, and as a result, the platen has a substantially orbital reciprocation. The other end of the rod is provided with a hook to facilitate retraction of the rod away from the pivot arm. In this position, the pivot arm is unrestrained, and the platen has a substantially straight-line reciprocation. One other prior art concept employs a tapered socket on the free end of the pivot arm and a correspondingly tapered locking member screw-threaded into a bracket mounted on top of the platen. The locking member may then be turned by means of a key -for the purpose of engaging the socket and thereby restraining the free end of t'he pivot arm. In each of these prior art Patented Dec. 31, 1968 ICC designs, however, the clamping force is directed along a substantially horizontal direction, normal to the eccentric axis, and no means is provided in the clamping mechanism for slidably guiding the free end of the oscillating pivot arm in its unrestrained position.

Objects of the present invention therefrom; a pair of clamping washers piloted on the stud and straddling the free end of the pivot arm; and a lever having a threaded portion engaging the stud above the clamp washers. Preferably, the clamping washers are formed of an anti-friction material and are keyed together against relative rotation; moreover, the lever is engaged by a separable wrench, preferably molded of a plastic material, and having a recess which engages the en'd of the lever.

These and other objects of the present invention will become apparent from a reading of the following specification, taken in conjunction with the enclosed drawings, in which:

Description of the drawings FIGURE 1 is a side elevation of a typical portable power-operated abrading tool with which the teachings of the present invention may ind particular utility, the molded plastic wrench being shown in broken lines;

FIGURE 2 is an enlarged top plan view of the platen assembly7 with the conventional rubber posts to resiliently mount the platen to the housing of the tool being shown in section;

FIGURE 3 is a longitudinal section, taken along the lines 3 3 of FIGURE 2, the rubber posts being omitted for clarity of illustration; and

FIGURE 4 is an exploded perspective of the platen assembly of FIGURE 2, showing the oscillating pivot arm, the manner in which one end of the arm is pivotably mounted to the platen, and the improved structure of the present invention for slidably guiding and selectively restraining the free end of the pivot arm.

Detailed.l description With reference to FIGURE 1, the typical portable power-operated abrading tool 10` comprises a motor housing 11, a lower housing or skirt 12, a rear handle 13 provided vvith an electric switch 14 for energization of the tool from a line cord 1'5, a front control hanfdle 16, and a platen assembly, the latter being disposed below the skirt 12 and being indicated generally as at 17.

With reference to the remaining drawings, the platen assembly 17 includes a platen member or pad 18, which is provided with a sheet metal backing 19. The platen assembly is resiliently mounted to the tool by means of four rubber posts 2G. Each post has a lower anged collar 20A trapped against the pad by means of a bracket 21. One bracket is provided for each pair of posts. The bracket 21 'has slotted openings 22 receiving lanced-out raised tabs 23 to position or locate the bracket on the pad. The bracket 21 is further provided with circular openings 24 receiving the respective posts 20, and the bracket is secured to the pad by means `which includes a screw 25. In this manner, each bracket 21 traps the respective anged collars 20A of a pair of rubber posts 20. Moreover, each bracket has a curved extending portion 26 which journals a cylindrical rod 27. The rod 27 has a plurality of spaced-apart knurled sections 28 and a screwdriver slot or kerf 29 at either end thereof. This construction provides a convenient clamp for the typical abrasive paper used in conjunction wilh a tool of this type. The function of the rubber posts, the manner in which they are trapped against the pad 18 by means of the bracket 21, the manner in which the upper portions of the posts are secured to the housing of the tool, and the formation of the paper clamp subassembly, comprises no part of the present application, but rather is described more particularly in the :zo-pending Enders application, Ser. No. 348,124, led Feb. 28, 1964, entitled Oscillating Platen for Abrading Tool, and assigned to the assignee of the present invention, now Patent No. 3,336,702, dated Aug. 22, 1967.

In accordance with the teachings of the present invention, an oscillating pivot arm 30 is disposed between the housing and the pad 18. One end of the pivot arm 30 is pivotably mounted on the pad; the intermediate portion of the pivot arm carries a bearing for journaling a driving eccentric; and the free end of the pivot arm is slidably guided and selectively restrained for converting the straight-line reciprocation of the pad into an orbital reciprocation.

With particular reference to FIGURES 3 and 4, one of the screws 25 (for the respective bracket 21) secures an internally-threaded stud 31 to the pad. The stud 31 has a flanged portion 31A supporting a bushing 32. Preferably, the bushing 32 is molded from a suitable anti-friction plastic material. The end of the pivot arm 30 has a collar portion 30A supported on the bushing 32. A retainer washer 33, which also may be made of a suitable antifriction plastic material, is mounted above the collar 30A on the pivot arm. The structure is prevented from disassembly by means of a screw 34 and washer 35, the screw 34 being received -within the remaining portion of the threaded stud 3i. In this manner, the front end of the pivot arm 20 is journaled for pivotal movement relative to the pad the platen assembly.

Any suitable means may be provided for driving the pivot arm 30. However, in the preferred embodiment, a bearing retainer 36 is secured to the pivot arm 30, intermediately its ends, by means of screws 37. The bearing retainer 36, see FIGURE 3, has a seat 36A for a spherical bearing 38. The bearing 38 journals a driving eccentric 39 along a substantially vertical axis. As a result, the pivot arm 36 oscillates in a substantially horizontal plane above the pad 18, and the pad 18 has a substantially straight-line reciprocation. The driving eccentric means described herein forms no part of the present invention, but rather, is described in detail in the Enders Patent 3,199,251 entitled Driving Mechanism for Abrading Tool, issued on Aug. 10, 1965, and assigned to the assignee of the present invention.

The improved structure of the present invention for slidably guiding the free end of the pivot arm 30 and for selectively restraining the free end by means of a clamping force exerted along a vertical plane (or direction) which is parallel to the vertical axis of the driving eccentric, is as follows: A threaded stud 40 is secured to the pad by means of one of the screws 25. A pair of clamp washers (comprising a top clamp washer 41 and a bottom clamp washer 42) are piloted on the unthreaded portion of the stud 40. The clamp washers are made of an anti-friction material, such as a suitable molded plastic, and are adapted to straddle the raised lip portion 3GB formed on the free end of the pivot arm 30. The top clamp washer 41 has a tongue 43 received within a recess 44 formed in the bottom clamp washer 42. As a result, the clamp washers are keyed together against relative rotation. Moreover, the bottom clamp washer 42 has ears 42A which straddle the bracket Z1, thereby preventing rotation of the clamp washers relative to the bracket and hence to the stud 40. A lever 45 has a threaded portion 46, such as a weld nut, for engaging the stud 4t) above the clamp washers. Completing the assembly, a washer 47, O-ring 48, washer 49, and screw 5t), the latter being threaded into the stud 40, retain the clamp washers and the lever against disassembly from the stud 40.

Operation In operation, the lever 45 and the weld nut 46 carried thereby may be pivoted (preferably through an acute angle) for clamping the washers 41, 42 against the raised lip 30B on the pivot arm 39, as shown in the position of FIGURE 2. As a result, a vertical clamping force is exerted on the free end of the pivot arm 39; the free end of the arm 30 is restrained against further oscillation in a horizontal plane above the pad; and the substantially straight-line reciprocation of the pad is converted into an orbital reciprocation. Orbital reciprocation of the pad facilitates a relatively higher work removal, while straight-line reciprocation facilitates a smoother finish on the work. When the lever 45 is pivoted in the opposite position, the free end of the pivot arm 30 is unrestrained, yet is slidably guided between the anti-friction material of the pair of clamp washers 41, 42.

F or operator convenience, the lever 45 may be actuated by means of a wrench 51, The wrench 51 has a recess 52 which engages the end 45A of the lever. Preferably, the wrench is economically formed as a molded plastic piece, and may be carried on the line cord for the tool.

Obviously, many modifications may be made without departing from the basic spirit of the present invention; and accordingly, within the scope of the appended claims, the invention may be practiced other than has been specically described herein.

I claim:

1. `In a portable power-operated abrading tool, the combination of a housing, a platen below the housing, means resiiiently mounting the platen to the housing, a pivot arm between the housing and the platen, the pivot arm having a pair Vof ends, one of `which is pivotably mounted on the platen and the other of which is free and is normally unrestrained, a driving eccentric disposed along a vertical axis and operatively connected ywith the pivot arm between the ends of the arm, whereby the pivot arm oscillates in a horizontal plane above the platen, and whereby the platen has a straight-line reciprocation, a combined guiding and selective clamping means mounted on the platen beyond the free end of the pivot arm, said combined guiding and selective clamping means slidably receiving the free end of the pivot arm, thereby supporting the free end of the pivot arm in its unrestrained position, and said combined guiding and selective clamping means having manually-actuated means integrally included therein for selectively vertically clamping the free end of the pivot arm in a plane substantially parallel to the vertical axis of the driving eccentric and offset radially therefrom, whereby the free end of the pivot arm is restrained against further horizontal oscillation, and whereby the straightline reciprocation of the platen is thereby converted to an orbital reciprocation.

2. In a portable power-operated abrading tool, the combination of a housing, a platen below the housing, means resiliently mounting the platen to the housing, a pivot arm between the housing and the platen, the pivot arm having a pair of ends, one of which is pivotably mounted on the platen andthe other of which is free and is normally unrestrained, a driving eccentric disposed along a vertical axis and operatively connected with the pivot arm between the ends of the arm, whereby the pivot arm oscillates in a horizontal plane above the platen, and whereby the platen has a straight-line reciprocation, means slidably guiding the free end of the pivot arm in its unrestrained position, and selective means vertically clamping the free end of the pivot arm in a plane substantially 6 parallel to the -vertical aXis of the driving eccentric and (A) a pair of anti-friction clamping members, keyed offset radially therefrom, whereby the free end of the together against relative rotation, straddling the free pivot arm is restrained against further horizontal oscillaend of the pivot arm and slidably guiding the arm in tion, and whereby the straight-line reciprocation of the its unrestrained position; platen is thereby converted to an orbital reciprocatio-n; 5 (B) means including a movable mem-ber engaging at said selective means vertically clamping the free end of least one of the clamp members for bringing the the pivot arm comprising: members together in a yvertical direction, thereby re- (A) a threaded stud secured on the platen and projectstraining the arm; and

ing vertically therefrom; (C) a manually-manipulatable member, separable from (B) a pair of clamp washers piloted on the stud and 10 the tool, and selectively engaging at least a portion straddling the free end of the pivot arm; and of the movable member. (C) a lever having a threaded portion engaging the stud above the clamp washers. References Cited 3. The combination of claim 2, wherein: UNITED STATES PATENTS (A) the. clamp washers are formed of an antifriction 15 2 697 898 12/1954 Osman 51 170 iiierral and are keyed together against relative rotag gg 00?? ms en 4. The combmatlon of claim 2, wherein. 2,885,833 5/1959 Neff 51 170 (A) a molded plastic wrench has a recess engaging the end of the lever. 20 r5. The combination of claim 1, wherein said combined LESTER M' SWINGLE Primary Examiner' guiding and selective clamping means comprises: 

